Manufacture of thermionic valve grids



Bea- 10, 1963 Q L E ETAL I 3,113,596

MANUFACTURE OF THERMIONIC VALVE GRIDS Filed Jan; 15, 1959' emu 70 0779/1 071/944 BY ""m' United States Patent ()fifice Patented Dec. 10, 1963 MANUFACTURE 6F THERMIQNIC VALVE GRHDS Clayton Arhuthnot Lane, Enfield, and Reginald John,

Edmonton, London, Engiand, assignors to Assoeiated Electrical Industries (Weolrich) Limited, Londen, England, a British company Filed Jan. 13, 1959, Ser. No. 786,539 Ciaiins priority, appiication Great Britain .lan. 16, 1958 2 Ciaims. (Cl. Mai-J15) This invention relates to the manufacture of grids for thermionic valves.

It has been the usual practice to produce a shaped grid for a thermionic which is both accurately circular and in which the working part of the grid is accurately central with reference to the support wires.

It is an object of the present invention to provide a method of and apparatus for forming a grid accurately.

grid wire around two spaced apart support wires and a mandrel having fins extending between the two wires and then pressing a forming tool around the wound grid to make the grid wire follow the outline at least of the fins.

In another aspect of the present invention apparatus for forming a grid for a thermionic valve comprises a mandrel having fins extending radially outwards on rerespectively show inaccuracies progrid in accordance of the grid is accurately dimensioned, for instance by being circular as shown in the figure. To produce this shape the grid wire 1 is placed fairly loosely around the and 3 between which is positioned a circular mandrel 4 as shown in FIG. 2. To form the grid two outer tools 5 and 6 are then applied to either side or" the mandrel to force the wires to take up the shape shown in FIG. 1. With such a method the grid may not always be accurately circular around the manin accordance with the present invention therefore a finned mandrel 7, as shown in FIG. 4 is used. The fins and M of the mandrel extend between the two sup- Outline of the mandrel, the fins and the support wires. In addition tools it and 9 ensure that the mandrel is maintained centrally of the support wires. Adequate clearance is provided between the circular par-t of the mandrel and the forming tools to prevent flattening 0f the grid wire over the working section.

The finned mandrel also has the advantage of holding the support wires at predetermined fixed positions so as it is formed, thus working section.

The invention not only applies to working sections but working section as in FIG. 5.

What we claim is:

1. A method of forming a grid for a thermionic valve comprising the steps of forming a wire into a helix, loosegrids having circular may be applied to any shape of for instance shown at 1%, 11 and 12 port wires, and then applying pressure to the wound grid only, by means of two forming said central region, to

thereby be stretched over said central region.

2. The method of claim 1 wherein said grid wires are stretched beyond their elastic limit.

References Cited in the file of this patent UNITED STATES PATENTS 2,064,169 Kershaw Dec. 15, 1936 2,379,135 Ekstedt et al June 26, 1945 2,429,062 Johansen Oct. 4, 1947 2,794,934 Eisan June 4, 1957 2,812,499 Robertson Nov. 5, 1957 2,880,496 Benedict et a1. Apr. 7, 1959 2,989,019 Van Sciver June 20, 1961 UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent Nor. 3 113596 December 10 1963 Clayton Arbuthnot Lane et al It is hereby certified that error appears in the above numbered patent requiring correction and that the said Letters Patent should read as corrected below.

In. the grant lines 2 and 3 and 13 and in the heading to the printed specification lines 4 and 5 name of assignee for "Associated Electrical Industries (Woolrich) Limited", each occurrence read Associated Electrical Industries (Woolwich) Limited --a Signed and sealed this 5th day of May 19640 (SEAL) Attcst:

ERNEST WU SWIDER EDWARD J: BRENNER Attesting Officer Commissioner of Patents 

1. A METHOD OF FORMING A GRID FOR A THERMIONIC VALVE COMPRISING THE STEPS OF FORMING A WIRE INTO A HELIX, LOOSELY PLACING THE HELICALLY WOUND GRID WIRE AROUND TWO SPACED APART SUPPORT WIRES, INSERTING INSIDE THE GRID BETWEEN SAID TWO WIRES A MANDREL HAVING A SHAPED CENTRAL REGION AND A PAIR OF FINS EXTENDING RADIALLY OUTWARDS ON OPPOSITE SIDES OF SAID CENTRAL REGION, SAID FINS BEING IN EDGE CONTACT WITH AND IN A PLANE BETWEEN THE SAID SUPPORT WIRES, AND THEN APPLYING PRESSURE TO THE WOUND GRID IN THE VICINITY OF THE FINS ONLY, BY MEANS OF TWO FORMING TOOLS HAVING CLEARANCE AROUND SAID CENTRAL REGION, TO CAUSE THE GRID WIRES TO FOLLOW THE OUTLINE OF THE FINS AND THEREBY BE STRETCHED OVER SAID CENTRAL REGION. 